Minanu Technologies

Build Your Own Phone Using a Raspberry Pi:

PiPhone – A Raspberry Pi based Smartphone

A smartphone based on a Raspberry Pi. It’s called – wait for it – the PiPhone. It makes use an Adafruit touchscreen interface and a Sim900 GSM/GPRS module to make phone calls. It’s more of a proof of concept to see what could be done with a relatively small form factor with off-the-shelf (cheap) components.

What makes this different from the Timelapse controller is the addition of a a SIM900 GSM module, which is connected via UART to the Raspberry Pi. Also, got a LiPo battery that would fit nicely between the TFT screen and the Raspberry Pi, so it could be used standalone, without any wires hanging off it whatsoever. Here’s the finished PiPhone.

The touchscreen interface developed for the purpose of this project. It’s a numeric keypad, with a display of the number to dial at the top, and a phone icon at the bottom to make or hang up the call.

Once we turn the unit over, we can see the main communications module, which is a Sim900 GSM/GPRS module. This allow us to send standard AT commands to it to make calls, hang up, send texts, data etc. Overall a very clever module. Towards the bottom of the white PCB, you can see the SIM Card, which allows the module to associate with my local GSM network, and it’s using a regular prepaid SIM card,the on.off switch and a DC-DC converter, which converts the 3.7volts from the LiPoly battery to 5volts needed by everything else. The DC-DC converter.

Which fits nicely between the TFT and the Pi. The only problem with this setup is heat. It gets a bit warm around the CPU if you leave the unit switched on for several minutes, as there’s very little air circulation. With a small fan circulating the air around it, was able to leave it on for extended periods during development, and it was cool to the touch.

Also, the 6 pin header on the GSM module sticks out a bit, so though about de-soldering the header and soldering the wires directly onto the PCB. That would prevent the connector sticking out so much, and would sit better when placed on a flat surface.

And the other side view, showing the foam-core board seperating the GSM module from the Raspberry Pi.Choose a nice thick piece to ensure no electrical connections between them.And a couple of well placed cable-ties was all that was needed to hold everything together.

Components and their Costs:

Raspberry Pi Model B – Rs.3290.00
PiTFT Touchscreen 320×240 – Rs.2071
2500mAh LiPo battery – Rs.888
SIM900 GSM/GPRS module – Rs.2841
DC-DC boost converter 3.3V – 5V 1A – Rs.592
Cables, connectors, switch, etc. - Rs.592
Total: Aprx Rs. 9500

Software

Code is available on GitHub. All the instructions are there, and links on what to do to install the PiTFT, etc.